The present invention relates to an apparatus and method for attaching nut inserts to a workpiece, the workpiece having a first side and a second. Usually the first side is a visible side and the second side is a blind side, meaning there is no access to the second side. More particularly, this invention relates to an installation system which is capable of expanding the body of the insert such that the insert cannot be withdrawn from an aperture within the workpiece, while, nearly simultaneous to the expanding of the body of the insert, the system fuses the flange portion of the insert to the first side of the work piece, through a fusing process such as resistance welding or capacitor discharge welding.
It is known to use threaded rivet nuts, threaded inserts, and threadable inserts, as anchors for threaded fasteners in a number of different applications, including thin wall applications, such as sheet metal, which may be too thin to be tapped with threads. In many such cases there is access only to one side of the workpiece. In general, the workpiece is drilled or punched and the anchor device is placed within the resulting hole by an installation tool. With the known installation tools, when the tool is activated, a portion of the anchor device on the blind side of the workpiece, such as a sleeve portion, is deformed to create an enlargement which prevents removing the insert from the hole. After the installation tool is remove, a threaded fastener may be inserted into a threaded portion of the insert.
Installation tools for setting nut inserts, particularly in blind applications, are known. These tools generally comprise a tool body from which extends a stud member having external threads. A pull rod is connected to the rear of the stud member, where the pull rod is connected to means within the tool body for reciprocating the stud member. The stud member typically extends through a nose piece which is connected to the front of the tool body. There are means within the tool body for rotating the stud member. An insert is screwed onto the external threads of the stud member, and the stud member made up into the insert until a flange on the end of the insert abuts the front end surface of the nose piece. The insert is thereafter placed within an aperture in the workpiece until the flange abuts the first side of the workpiece. The pull rod is then retracted rearwardly a predetermined stroke so as to expand a tubular portion of the insert which is on the second side of the workpiece. The linear force on the insert causes the sleeve of the insert to plastically deform, such that the expanded portion, sometimes referred to as the “bubble”, is larger than the diameter of the aperture, preventing withdrawal of the insert from the aperture. Examples of such tools may be found in U.S. Pat. Nos. 4,070,889; 4,368,631; 4,612,793; 4,574,612; 5,605,070; and 6,272,899.
It is desirable that the anchor device resist spinning or rotating within the aperture in the workpiece. One known means of preventing rotation of the anchor device within the hole of the workpiece is to make the hole in a shape other than round, such as octagonal, and to use an insert having a sleeve which has a corresponding shape, such that the sleeve is locked within the hole to prevent rotation, as the corners of the sleeve lock into corresponding corners of the hole. However, installing non-round openings in the workpiece and manufacturing inserts having other than a round shape is more costly than installing round openings in the workpiece and manufacturing round inserts.